I remember seeing store-bought metal templates years ago, but I don't believe they had a built in blade (I think you used a razor knife).

For the bulk loading I've been doing, I just quickly do a straight cut at something a bit less than 45 deg and going back about 2 inches. I do try to end the cut in between perferations but I don't try to imitate a "factory" leader. It's fine for my Nikon and Olympus bodies and just takes a second.

I haven't noticed any problem with stray bits of film. Maybe I've been lucky.